The object of the proposed investigation is to determine the factors, cellular and systemic, which influence the magnitude and composition of the fluid secreted by the lacrimal gland and the contribution of that fluid to conjunctival fluid (tears) under a variety of conditions. To achieve this objective, the study includes experiments, which are designed to determine whether: the present hypotheses of the mechanism of secretion of electrolytes and water are correct; which, if any, of the substances in the fluid are actively transported; autonomic nerve impulses alter the composition of the fluid in the same manner as do autonomic drugs; various hormones alter the composition and/or magnitude of the secretion. An understanding of the mechanism and the control of secretion by the lacrimal gland as well as knowledge of the contribution of the lacrimal gland to tears should be useful in understanding local disrders of the cornea since the integrity of the cornea is, in part, a function of the fluid which bathes it. In addition, since the orbital glands, including the lacrimal, are the least understood of all the orbital glands, knowledge gained from this study should aid in understanding those systemic disorders, which are associated with abnormalities of the exocrine glands whether or not there is clinical evidence of abnormal lacrimation. This study, therefore, includes a clinical portion, in which the compostion of tears is correlated, not only with tear flow rate and ocular examination but also a variety of epidemiological factors in such diseases as Cystic Fibrosis, Sjogren's Syndrome, Familial Dysautonomia and Mikulicz Disease.